"No ad should ever discourage voters from voting or expressing their opinions at the ballot box," Angle's spokesman Jarrod Agen said in a statement to ABC News.

Angle said in a radio interview today that not encouraging voters to come out would be "exactly the wrong thing to do in this election."

Sen. Harry Reid's campaign had blasted Angle's silence on the issue as "reprehensible," and the Senate majority leader accused her of "trying to keep people from voting."

"The fact that Sharron Angle refused to speak out against these truly abhorrent tactics should tell all Nevadans, and especially the Hispanic voters she'd prefer be silenced, everything they need to know about why she's unfit to represent our state in the U.S. Senate," Reid's spokesman Kelly Steele said in a statement.

The "Don't Vote" ad, made by a little-known group called Latinos for Reform, encourages Hispanics stay away from the polls as a way to send a message to Democrats.

"Clearly, the Democratic leadership betrayed us," the English-language ad goes. "And now, when they need our votes, they are at it again with more empty promises."

"This November, we need to send a message to all politicians. If they can't keep their promise on immigration reform, then they can't count on our vote. Democratic leaders must pay for their broken promises and betrayals," it continues. "Don't vote this November. This is the only way to send them a clear message. You can no longer take us for granted. Don't vote."

Robert de Posada, the group's head, says the ad doesn't specifically target Democrats, but no Republican lawmakers are shown in either the English or the Spanish-language ads.

Hispanic groups from around the country were quick to denounce the effort. The National Association of Latino Elected and Appointed Officials said, "It is the height of cynicism to encourage voters to make themselves irrelevant by not exercising their right to be heard. This harkens back to attempts earlier this year at having Latinos boycott the U.S. Census."

The Las Vegas Latin Chamber of Commerce said it was "disheartened by the ads."

"We encourage all eligible community members to participate in the election and voting processes. We have worked very hard over the years to promote Hispanic participation in the voting process and were disheartened by the ads produced by Latinos for Reform that discouraged voting. We are pleased that the ads have been stopped," Luis Valera, chairman of the Las Vegas Latin Chamber of Commerce's board, said in a statement to ABC News.

The Hispanic vote is crucial to Reid's campaign. Hispanics make up more than a quarter of Nevada's population, according to the U.S. Census Bureau, and comprise 14 percent of all eligible voters in Nevada this year.

Ad Urging Hispanics Not to Vote Causes Uproar

De Posada served as the Republican National Committee's director of Hispanic affairs from 1989 to 1993, according to his resume. He also served as one of three directors for Americans for Border and Economic Security with former GOP Rep. Dick Armey, who now runs a leading Tea Party group, FreedomWorks. De Posada also served in the Bush administration and as an advisor to former Republican Sen. George Allen of Virginia -- who lost his reelection bid in 2006 after he was accused of using a racial slur against one of his opponent's aides.

In 1994, de Posada helped created the Hispanic Business Roundtable, which later changed its name to The Latino Coalition.

According to campaign records, De Posada also has been a longtime contributor to Republican candidates.

Reid accused Angle of backing the ad, but in a radio interview with conservative talk show host Heidi Harris today, Angle denied any link to de Posada, saying she has "absolutely nothing" to do with the ad.

"I know that there's an ad out there by an independent expenditure of some kind that has been saying that we don't want to turn out voters, but yes we do, every voter," she said. "If someone wants to spend money, they can, and you don't, you can't collaborate. You can't coordinate. You can't talk to them about it."

Hispanics Crucial to Harry Reid

Hispanic voters turned out overwhelmingly in favor of Obama in 2008, and minorities in Nevada were overwhelmingly credited with helping push the Democrats to victory.

Based on analysis by Brookings Mountain West at the University of Nevada, Hispanics have a far more favorable view of the president and his party than whites do.

"I don't think it's a surprise that Nevada was targeted for this ad," said John Tuman, chair of the political science department and director of the Latin American Studies Program at the University of Nevada, Las Vegas. "If the ad depressed the Latino vote it could certainly tip the race in favor of Angle, given how close it is."

And while immigration registers as the fourth top priority for whites, it's not a top-five priority for Hispanics, according to the UNLV survey.

There is concern among Hispanics in Nevada about the lack of progress on immigration reform but the ad hasn't been viewed very favorably in the state, Tuman said.

Democrats have aggressively courted Hispanic voters through the years. In 2008, they sponsored a soccer team called "Los Democratas." They have supported labor unions dominated by Hispanics, like the Nevada culinary union.

Angle defended images in those ads of dark-skinned men coming across a fence. To illustrate to Hispanics that ethnicities can be mixed up, Angle told Latino students last Friday that some of them could even be mistaken as Asian.

"What we want is a secure and sovereign nation and, you know, I don't know that all of you are Latino. Some of you look a little more Asian to me. I don't know that," Angle said at the event, organized by the Hispanic Student Union and with only Hispanic students in attendance. "What we know about ourselves is that we are a melting pot in this country. My grandchildren are evidence of that. I'm evidence of that. I've been called the first Asian legislator in our Nevada State Assembly."